JP6469811B2 - Corrosion erosion prevention structure, pump including the same, pump manufacturing method and repair method - Google Patents

Description

  The present invention relates to a pump using a casing ring (liner ring), and in particular, a pump impeller has a radially inward flow with respect to a rotating shaft such as a double suction centrifugal pump, a centrifugal multistage pump, a pump having a suction volute, and the like. The present invention relates to a structure for preventing corrosion and erosion in a casing ring (liner ring) and a pump including the same. Furthermore, it is related with the manufacturing method and repair method of the said pump.

  The pump casing ring (liner ring) and the impeller ring (wear ring) are present at the boundary between the high pressure portion and the low pressure portion of the pump impeller. The casing ring is fixed to the casing and does not rotate, while the impeller ring rotates according to the rotation of the rotating shaft. For this reason, the casing ring and the impeller ring are basically designed not to contact each other, and a slight gap is provided between them.

  For example, FIG. 10 is a general type of pump in which a radially inward flow flows into the injection portion 59a of the impeller 59. A prime mover such as an electric motor (not shown) is engaged with the rotary shaft 57 of the pump. The impeller 59 is rotated by the driving force of the prime mover. The liquid flowing through the suction-side flow channel 61 flows inward in the radial direction from the radially outer side of the rotating shaft 57 and flows into the impeller 59a of the impeller as indicated by an arrow C in the drawing.

  The liquid that flows into the impeller 59 from the suction side flow path 61 receives the rotational energy of the impeller 59 and becomes a liquid whose pressure energy and kinetic energy are increased by centrifugal force. In order to maintain this pressure energy, a part of the casing 53 is formed as a partition wall 65 so as to separate the suction side flow path 61 and the discharge side flow path 63.

  A casing ring 69 is provided at an end of the partition wall 65 of the casing 53, at a portion facing the impeller 59 (sliding in some cases). On the other hand, an impeller ring 60 is provided on the impeller 59.

  As another example, FIG. 11 is a cross-sectional view showing an example of both suction centrifugal pumps 101. 11 includes an upper casing 103, a lower casing 105, a rotating shaft 107 installed in a boundary region between the casings 103 and 105, and an impeller installed on the rotating shaft 107. 109. A suction side flow path 111 and a discharge side flow path 113 are formed in both casings 103 and 105 via an impeller 109.

  The impeller 109 rotates with the rotation of the rotating shaft 107 with which a prime mover such as an electric motor (not shown) is engaged. By this rotation, the impeller 109 sucks the liquid from the suction side flow paths 111 on both sides around the discharge side flow path 113. For this reason, in the suction side flow path 111, the radially inward flow flows into the injection portion 109 a of the impeller 109. The rotational energy of the impeller 109 is given to the liquid as a centrifugal force, and converted into pressure energy and kinetic energy of the liquid itself. In order to maintain this pressure, a part of the casings 103 and 105 is formed as a partition wall 115 so as to separate the suction side flow path 111 and the discharge side flow path 113.

The end of the partition wall 115 of the casings 103 and 105 and the part that slides with the impeller 109 is described in detail in FIG. 12, which is an enlarged view of the region A in FIG. As shown in FIG. 12, the casing ring 119 is provided in the partition wall 115 which is a part of the casing 105 and the impeller ring 110 is provided in the impeller 109 in the positional relationship described above. Needless to say, the same structure as that of the region A is also present in a portion symmetric with respect to the rotation axis and a portion symmetric with respect to the center line L in the drawing.

  As described above, in the illustrated pump 101, at a portion where the casing ring 119 and the impeller ring 110 are opposed to each other, a leakage flow passing through a gap between the two occurs from the high pressure side to the low pressure side. Since this gap is designed to be very small, it is inevitable that the two come into contact with each other. Therefore, the casing ring 119 is not required to have the performance required for the bearing. However, if the casing ring 119 is lubricated by the liquid sent by the pump 101, a material that does not cause a problem even if contacted is selected. For this reason, since the material of the casing ring 119 is selected, in many cases, the casing 105 and the casing ring 119 are a combination of different metal materials.

  By the way, when the two different metals are in electrical contact with each other and come into contact with the electrolyte solution, corrosion is promoted as compared with the case where it is alone. This is a corrosion phenomenon caused by electrons moving from a metal having a strong ionization tendency to a weak metal due to a potential difference between the metals, and the metal atoms that have lost their charge are dissolved in the solution as ions. For example, cast iron, which is widely used as a material for pumps, corrodes at a rate of about 0.1 to 0.2 mm per year when exposed to water containing a large amount of dissolved oxygen. However, when the cast iron is in electrical contact with a (noble) metal having a higher corrosion potential than cast iron such as stainless steel, the corrosion is further accelerated, and in some cases more than twice that when cast iron is present alone. Corrosion rate may be reduced. For this reason, a gap may be generated due to corrosion between the casing and the casing ring that have been operated for a long time.

  In conventional pumps, there are many cases in which the casing ring and the casing are in direct contact with each other between the metal processed surfaces without painting. For example, if the casing is cast iron and the casing ring is a combination of stainless steel, the corrosion rate of a single cast iron is 0.1 mm / y, and the rate of promotion by contact with stainless steel is doubled. In some cases, a gap of about × 2 × 10 = 2 mm is formed between the casing and the casing ring. As described above, the casing ring exists between the high pressure portion and the low pressure portion in the pump. For this reason, the clearance gap between a casing and a casing ring expands, a high pressure part and a low voltage | pressure part are connected, and the fluid will pass the clearance gap. As a result, a new leakage flow is generated separately from the leakage flow between the casing ring and the impeller ring.

  Furthermore, when the pump head is high, the pressure difference between the high-pressure side and the low-pressure side becomes large, and the speed becomes extremely high when the leakage flow is ejected to the low-pressure side. This causes cavitation around the casing ring. Since cavitation erodes the metal material, it may cause erosion on the surface of the casing in the vicinity thereof, including the portion where the casing ring and the casing come into contact.

  In particular, in cast iron widely used as a pump material, the surface damage is significant when such dissimilar metal contact corrosion and cavitation erosion are superimposed. As the leakage flow increases and casing damage progresses, the performance required for the pump cannot be satisfied. In addition, the strength of the pump casing is reduced, and the possibility that a larger scale of the pump will be damaged increases.

In addition, the pump often has an “inlet backflow” accompanied by cavitation in the impeller portion at a low flow rate. This is because the flow rate is limited by opening and closing a valve installed on the downstream side of the impeller. This inlet backflow phenomenon is a flow in which the fluid recirculates from the inside of the impeller 59 to the suction side flow path 61 as shown in FIG. Since the reverse flow of the inlet is also close to the casing ring 69, it also contacts the partition wall 65 close to the casing ring 69 and further promotes erosion.

  However, there is no known prior art that prevents surface damage due to cavitation erosion combined with corrosion between the casing and the casing ring (liner ring). For this reason, this invention is made | formed in view of the said problem, Even if a casing and a casing ring are dissimilar metal materials, generation | occurrence | production and progress of corrosion between each other material are prevented. Moreover, the structure which prevents the cavitation erosion by the leakage flow in the clearance gap produced between a casing and a casing ring is provided. Furthermore, the present invention provides a structure that prevents erosion of the casing (partition wall) in the vicinity of the casing ring due to the influence of “inlet backflow” that occurs with cavitation in the impeller at a low flow rate of the pump.

  The first means for solving the problem is an erosion prevention structure in the vicinity of a facing portion between the casing and the impeller, the casing, a casing ring that is installed in the casing and faces the impeller, and the casing And an electrically insulating material provided between the casing ring and the casing ring. By doing in this way, between an casing ring and a casing is electrically insulated by an electrical insulating material, the dissimilar-metal contact corrosion between a casing ring and a casing does not arise, but progress of corrosion is suppressed. Further, the electrically insulating material can prevent the pressurized liquid from flowing through the gap between the casing ring and the casing. For this reason, the erosion by cavitation and the increase of the leakage flow between the casing ring and casing resulting from them are prevented.

  A second means is the corrosion erosion prevention structure according to the means 1, wherein the electrical insulating material includes an epoxy-based material or a silicon-based material. When the pump is operated for a long period of time by sandwiching an electrical insulating material containing at least one of epoxy, silicon, and PTFE material between the casing and the casing ring, the vibration of the pump and the impact during sliding Even if there is frictional heat or the like, the electrical insulating material does not break or come off and maintains the adhesion. For this reason, while maintaining the gap between a casing and a casing ring so that the pressurized liquid may not distribute | circulate, the electrical contact and electrical conduction of a casing ring and a casing can also be prevented.

  The third means is the structure for preventing corrosion and erosion according to means 1 or 2, wherein an O-ring for sealing is disposed on the boundary surface between the casing and the casing ring. In this way, when the pump is operated over a long period of time, even if the electrically insulating material is cracked or peeled off from the casing ring or casing due to vibration of the pump, impact during sliding, frictional heat, etc. The o-ring maintains the sealing performance. For this reason, while keeping the pressurized liquid from flowing through the gap between the casing ring and the casing, electrical contact and electrical continuity between the casing ring and the casing can be prevented.

  The fourth means is any one of the means 1 to 3, wherein an outer edge extension extending from the portion facing the impeller toward the radially outward direction of the pump main shaft is provided on the low pressure side of the casing ring. It is a structure for preventing corrosion and erosion as described in the item. By doing in this way, the casing ring also spreads outward in the radius of the suction flow path, and the backflow cavitation does not directly hit the casing but is protected by the casing ring.

The fifth means is the corrosion erosion according to means 4, wherein the difference between the angle at the tip of the outer edge extension and the angle of the outer edge of the impeller facing the tip of the outer edge is within 10 degrees. It is a prevention structure. By doing so, the flow of the liquid becomes smooth and the loss caused by the step is reduced.

  Sixth means is the structure for preventing corrosion and erosion according to any one of means 1 to 5, wherein the casing ring is configured by combining two members. By doing so, even if the casing and the electrical insulating material have a complicated shape, it is possible to install a casing ring having a complicated shape correspondingly. Also, it is possible to easily install a casing ring having a complicated shape even in a pump in which the upper casing and the lower casing are not separated.

  Seventh means includes the corrosion erosion prevention structure according to any one of means 1 to 6, a pump main shaft rotatably supported by the casing, an impeller mounted on the pump main shaft, And a liquid channel formed inside the casing.

  The eighth means is a method of manufacturing a pump comprising a casing and an impeller, wherein the casing is provided, an electrical insulating material is provided at a predetermined location of the casing, and a predetermined casing ring facing the impeller is provided with the electric It is a manufacturing method of a pump installed in the casing via an insulating material.

  Ninth means is a method of repairing a pump comprising a casing and an impeller, wherein an electrical insulating material is provided at a predetermined location of the casing, and a predetermined casing ring facing the impeller is provided via the electrical insulating material. This is a method for repairing the pump installed in the casing.

By each means as described above, for example,
1) Prevention of corrosion between casing ring and casing,
2) Prevention of leakage flow between the casing ring and the casing due to the above corrosion,
3) Prevention of cavitation erosion due to leakage flow, and 4) Prevention of erosion near the pump casing ring due to cavitation of "inlet reverse flow" generated near the pump suction port at low flow rates.
It becomes possible to do.

It is a whole sectional view of a pump which comprises a corrosion erosion prevention structure concerning one embodiment of the present invention. It is an expanded sectional view in the field A of FIG. It is an expanded sectional view of another embodiment in the area | region A of FIG. It is an expanded sectional view of another embodiment in the area | region A of FIG. It is an expanded sectional view of another embodiment in the area | region A of FIG. FIG. 6 is an enlarged view of a portion B in FIG. 5. It is an expanded sectional view of embodiment in the pump of the form different from one Embodiment of this invention. It is an expanded sectional view of another embodiment in the pump of the form different from one Embodiment of this invention. It is an expanded sectional view of another embodiment in the pump of the form different from one Embodiment of this invention. It is whole sectional drawing which shows the conventional pump. It is whole sectional drawing which shows the conventional pump. It is an expanded sectional view of the area | region A of the pump disclosed in FIG. It is explanatory drawing of the "inlet backflow" accompanied by cavitation in the impeller part at the time of low flow volume.

  Next, an embodiment of the present invention will be described with reference to the drawings.

[Overview]
FIG. 1 is a cross-sectional view showing an overall outline of a double suction spiral pump 1 according to the present embodiment. The pump 1 includes an upper casing 3, a lower casing 5, a rotating shaft 7 installed in a boundary region between the casings 3 and 5, and an impeller 9 provided on the rotating shaft 7. A suction side flow path 11 and a discharge side flow path 13 are formed in both casings 3 and 5 via an impeller 9. The suction side flow path 11 and the discharge side flow path 13 are fluid flow paths.

[casing]
As described above, the pump 1 of the present embodiment is a double-suction centrifugal pump that sucks liquid from both sides around the discharge-side flow path 13. For this reason, the partition 15 which separates the suction side flow path 11 and the discharge side flow path 13 is provided in the casings 3 and 5. One of the features of the present embodiment is the structure in the vicinity of the end portion of the partition wall 15 of the casings 3 and 5 and the portion facing (sliding) the impeller 9. The facing portion is shown as region A in this figure.

[Axis of rotation]
A prime mover such as an electric motor (not shown) is engaged with the rotary shaft 7 of the pump 1. The impeller 9 installed on the rotary shaft 7 is rotated by the driving force of the prime mover. In the pump 1 of this embodiment, the rotating shaft 7 is provided along the horizontal direction. For this reason, the impeller 9 rotates along a vertical plane crossing the rotation shaft 7. However, the horizontal axis of rotation in this embodiment is an example, and it may be installed along the vertical direction or other angular directions. The rotating shaft 7 is sandwiched between the upper casing 3 and the lower casing 5 via a bearing 7a. The part where the bearing 7a is installed is basically a boundary between the suction side flow path 11 inside the pump and the external environment. For this reason, the bearing 7a is provided with a seal structure (not shown) so that the liquid in the suction side channel 11 does not leak to the outside.

[Impeller]
The impeller 9 rotates with the rotation of the rotary shaft 7 and sucks liquid from the suction side flow paths 11 on both sides around the discharge side flow path 13. The inflow portion 9a of the impeller 9 is formed in the vicinity of the rotating shaft 7, but the suction side flow path 11 is formed to the outside in the radial direction from the inflow portion 9a. For this reason, in the suction side flow path 11, the radially inward flow flows into the inflow portion 9 a of the impeller 9. The rotational energy of the impeller 9 is given as centrifugal force to the fluid flowing inside. This centrifugal force gives kinetic energy. As a result, the rotational energy of the impeller 9 is eventually converted into pressure energy and kinetic energy. Accordingly, the pressure in the discharge side flow path 13 is relatively higher than the pressure in the suction side flow path 11. In order to maintain this pressure, a part of the casing is provided as a partition wall 15 so as to separate the suction side flow path 11 on the low pressure side and the discharge side flow path 13 on the high pressure side.

  A casing ring 19 is provided on the partition wall 15 of the casing at the end of the partition wall 15 of the casings 3 and 5 and facing (sliding) the impeller 9 (region A in FIG. 1). A ring 10 is provided. This point will be described in detail in the explanation of enlarged views shown in FIGS. Needless to say, the same structure as that of the region A is also present in a portion symmetric with respect to the rotation axis 7 and a portion symmetric with respect to the center line L in the drawing.

[Casing ring]
As shown in FIG. 2, in the pump according to the present embodiment, the impeller 9 and the impeller ring 10 are substantially the same as the conventional one. On the other hand, the structure on the casing side is different from the conventional pump. That is, the electrical insulating material 17A is provided between the casing ring 19 and the end of the partition wall 15 of the casing. The electrical insulating material 17 </ b> A of the present embodiment has a semicircular shape, and is filled so as to be in close contact with the casing ring 19 and the partition wall 15. As described above, since the electrical insulating material 17A is in close contact with the casing ring 19 and the partition wall 15, no gap is formed between the casing ring 19 and the partition wall 15, and no leakage flow occurs. Electrical contact can also be prevented.

  As the electrical insulating material 17A, a resin material such as an insulating film, an insulating paint, or an insulating adhesive can be used. Further, fiber reinforced plastics and particle reinforced plastics can also be used. Furthermore, in addition to the resin material, insulating low-melting glass, ceramic adhesive, or the like may be used. However, it is necessary to maintain the functions of maintaining electrical insulation, maintaining sealing properties, and maintaining dimensional accuracy against vibrations, shocks, temperature changes, and the like due to pump operation over a long period of time. For this reason, an epoxy-based, silicon-based, or PTFE-based electrically insulating material is preferable as a suitable material. Even when these materials are used in water, there is almost no outflow or absorption of components into the water, so that there is almost no deterioration even when used over a long period of time.

  When the epoxy-based or silicon-based electrically insulating material is a liquid or gel-like insulating paint or insulating adhesive, adhesion (affinity) to the metal surface is good. For this reason, when an electrically insulating material is applied to at least one of the partition wall 15 and the casing ring 19 of the casing and the application surfaces thereof are aligned with the mating surface, the surface spreads to the mating surface of the casing partition wall 15 and the casing ring 19. A film-like layer of an electrically insulating material is formed between the two. This film-like layer becomes the electrical insulating material 17A of the present embodiment. This film-like layer gradually cures to some extent and becomes solid. The solid film-like layer has high adhesion strength and fracture strength. Therefore, when the pump is operated for a long period of time, even if there is vibration of the pump, impact during sliding, frictional heat, etc., the electrical insulating material 17A does not break or come off and maintains the adhesion. To do. For this reason, while maintaining so that the pressurized fluid may not distribute | circulate between the partition 15 and the casing ring 19 of a casing, the electrical contact and electrical continuity with the casing ring 19 and the partition 15 can also be prevented.

  In addition, if the electrically insulating material is silicon or PTFE, it is also preferable to form a film and sandwich it between the mating surfaces of the partition wall 15 and the casing ring 19. Since silicon (PTFE) does not lose viscoelasticity even when cured, it adheres closely to the metal surface if the surface roughness of the metal surface is small. Further, if the shape of the mating surface of the partition wall 15 and the casing ring 19 is standardized, it is possible to efficiently insert the silicon-based film between the partition wall 15 and the casing ring 19 in advance. Become. In this respect, there is no non-uniform application amount that tends to occur in the application of the insulating paint and the insulating adhesive. The thickness of the electrically insulating material filling is preferably in the range of 0.005 mm to 2 mm, for example, but 0.05 mm or more is preferably a film, and if it is less than 0.05 mm, an insulating paint or an insulating adhesive can be applied. preferable.

  In addition, in order to ensure the adhesiveness with the partition 15 and the casing ring 19, the cross-sectional shape of the electrical insulating material 17A is a rectangular wave shape. By doing so, even when an impact or the like is applied to the partition wall 15 or the casing ring 19, the electrically insulating material is prevented from peeling off from the partition wall 15 or the like. However, the cross-sectional shape is an example, and the present invention is not limited to this.

FIG. 3 is a diagram illustrating a second embodiment. This embodiment is a corrosion erosion prevention structure in which an electrical insulating O-ring is mounted in addition to the electrical insulating material 17. That is, an O-ring groove 23a is formed on the outer peripheral surface of the casing ring 19, and the O-ring 23b is fitted in the O-ring groove 23a. When the pump is operated for a long period of time, it is conceivable that the electrically insulating material 17B is broken or peeled off from the casing ring 19 or the casing 15 due to vibration of the pump, impact during sliding, frictional heat, or the like. Even in this case, the sealing performance can be maintained by the O-ring. For this reason, even if a gap is formed between the casing ring 19 and the partition wall 15, the sealing performance can be maintained so that liquid does not pass through the gap. At the same time, the casing ring 19 and the partition wall 15 of the casing are further reinforced so as not to make electrical contact.

  In the case of the embodiment using this O-ring, the O-ring is responsible for maintaining the sealing performance so as to prevent leakage flow. For this reason, the electrical insulating material 17B sandwiched between the mating surfaces of the casing ring 19 and the partition wall 15 is not required to have much adhesiveness with the mating surfaces. However, when an O-ring is used, it is assumed that the O-ring itself is crushed in order to ensure a certain level of sealing performance. In this case, the contact pressure between the casing ring 19 and the partition wall 15 is not uniform before and after the O-ring with the O-ring as a fulcrum (left and right of the O-ring in FIG. 3). For this reason, the electrical insulating material 17 sandwiched between the mating surfaces of the casing ring 19 and the partition wall 15 prevents the casing ring 19 and the partition wall 15 from being in contact with each other, and the contact pressure applied to these mating surfaces is reduced. In order to receive it, it is also desirable to mold it as a thickness of about 0.05 mm to 10 mm and fit it as a silicon or PTFE part.

  FIG. 4 shows a third embodiment. In this embodiment, the corrosion erosion prevention structure in which the outer edge of the casing ring 19 on the low pressure (suction side flow path 11) side extends radially outward of the rotating shaft is shown. Hereinafter, the extending portion is referred to as an outer edge extension portion 19A. An outer edge extension 19A on the low pressure side of the casing ring 19 covers the partition wall 15 of the casing in a wide range. By doing in this way, even if an inlet reverse flow accompanied by cavitation occurs from the impeller 9 to the suction side flow path 11 during the low flow operation of the pump, the casing ring 19 protects the partition wall 15 and thus prevents the progress of erosion. be able to.

  The outer edge extension 19 </ b> A extends outward in the radial direction with respect to the rotation axis with a diameter up to about 1.5 times the diameter of the inflow portion 9 a of the impeller 9. In the present embodiment, an electrical insulating material 17C having a predetermined thickness is also filled between the outer edge extension 19A and the partition wall 15. By forming such an outer edge extension 19A, the casing ring 19 is made of a metal resistant to erosion, for example, stainless cast steel, and the casing (partition 15) is less susceptible to erosion than stainless cast steel, but is a general-purpose metal. For example, even if it is made of cast iron, the partition wall 15 can be protected from cavitation erosion. In the case of a double-suction centrifugal pump or a pump having a suction volute, the suction flow path is not necessarily axisymmetric with respect to the rotation axis of the pump, but is often non-axisymmetric. It is desirable to manufacture the outer edge extension portion in a non-axisymmetric manner in accordance with the shape of the suction flow path so that the path and the outer edge extension portion 19A are smoothly connected.

  FIG. 5 shows a fourth embodiment. In this embodiment, the inclination of the outer edge of the casing ring 19 facing the inflow portion 9a side of the adjacent impeller 9 and the inflow portion of the impeller 9 at the low pressure side of the casing ring 19, that is, the outer edge of the suction side flow path 11 side. 9a is a corrosion erosion prevention structure in which the difference from the inclination of the outer edge facing the casing ring 19 side is within about 10 degrees (region B in the figure).

  FIG. 6 is an enlarged view of region B of FIG. In FIG. 6, the inclination angle of the outer edge of the casing ring 19 facing the inflow portion side of the adjacent impeller 9 is α ′ degree, and the inclination of the outer edge of the inflow portion of the impeller 9 facing the casing ring 19 side. The angle is α degrees. Here, by setting the angle so that the absolute value of α−α ′ is within 10 degrees, the flow of the liquid becomes smooth and the loss caused by the step is reduced.

  FIG. 7 is a diagram showing a main part of an example in which the structure for preventing corrosion and corrosion according to the present embodiment is applied to a pump of a type in which a radially inward flow flows into the inflow portion 9a of the impeller 9. The electrical insulating material 17E of this embodiment has an L-shaped cross section. A prime mover such as an electric motor (not shown) is engaged with the rotary shaft 7 of the pump, and the impeller 9 is rotated by the driving force of the prime mover. The liquid flowing in the internal flow path passes through the suction side flow path 11 between the side cover 14 and the partition wall 15 of the casing, and flows inward in the radial direction from the outside of the rotating shaft 7. Then, it flows into the inflow portion 9a of the impeller 9 as indicated by an arrow C in the figure.

  The liquid flowing into the impeller 9 from the suction side flow path 11 receives the rotational energy of the impeller 9 and is converted into a liquid whose pressure energy and kinetic energy are increased by centrifugal force. The pressure of the discharge side flow path 13 is relatively higher than that of the suction side flow path 11, and in order to maintain this pressure, the suction side flow path 11 and the discharge side flow path 13 are separated by the partition wall 15 of the casing portion. It is separated. In the pump of the present embodiment, since the rotary shaft 7 is provided along the horizontal direction, the impeller 9 rotates along a vertical plane that crosses the rotary shaft 7. However, the horizontal axis of rotation in this embodiment is an example, and it may be installed along the vertical direction or other angular directions.

  The casing ring 19 is provided on the partition wall 15 of the casing and the impeller ring 10 is provided on the impeller 9 at the end of the partition wall 15 of the casing and facing the impeller 9. An electrical insulating material 17 is provided between the casing ring 19 and the end of the partition wall 15 of the casing. The electrical insulating material 17E is filled so as to be in close contact with the casing ring 19 and the partition wall 15 of the casing. Has been. Since the electrical insulating material 17E is in intimate contact with the casing ring 19 and the partition wall 15, no gap is formed between the casing ring 19 and the partition wall 15, thereby preventing fluid leakage and preventing the casing ring 19 and the partition wall 15 from Electric contact can also be prevented.

  The electrical insulating material 17E may use any resin material such as an insulating film, an insulating paint, and an insulating adhesive, and may be formed as a fiber reinforced plastic or a particle reinforced plastic. In addition to resin materials, insulating low-melting glass, ceramic adhesive, and the like may be used. However, it is necessary to maintain the functions of maintaining electrical insulation, maintaining sealing properties, and maintaining dimensional accuracy by absorbing vibrations, shocks, and temperature changes in pump operation over a long period of time. For this reason, an epoxy-based, silicon-based, or PTFE-based electrically insulating material is preferable as a suitable material. Even when these materials are used in water, there is almost no outflow or absorption of components into the water, so there is almost no deterioration even during long-term use.

  The epoxy-based or silicon-based electrically insulating material has good adhesion (affinity) to the metal surface as long as it is a liquid or gel-like insulating paint or insulating adhesive. For this reason, when this is applied to one or both of the casing and the casing ring and the application surfaces thereof are aligned with the mating surface, the coating agent spreads on the mating surface of the casing and the casing ring, and an electrically insulating material is formed between the two. A film-like layer is formed. This film-like layer gradually cures to some extent and becomes solid. The solid film-like layer has high adhesion strength and fracture strength, and even when the pump is operated for a long period of time, even if there is vibration of the pump, impact during sliding, frictional heat, etc., the electrically insulating material Does not break or come off and maintains adhesion. For this reason, a gap is not formed between the casing ring and the casing, and the liquid is kept from leaking, and electrical contact and electrical continuity between the casing ring and the casing are prevented.

In addition, if the electrically insulating material is silicon or PTFE, it is also preferable to form a film and sandwich it between the mating surfaces of the casing and the casing ring. Since silicon or PTFE does not lose viscoelasticity even when cured, it adheres closely to the mating surface if the surface roughness of the mating surface is small. For this reason, if the shape of the mating surface of the casing and the casing ring is standardized, it is possible to efficiently insert the silicon-based film between the casing and the casing ring. In addition, there is no occurrence of non-uniform coating amount that tends to occur in the application of the insulating adhesive. The filling thickness of the electrical insulating material 17E is preferably in the range of about 0.005 mm to 2 mm, but 0.05 mm or more is preferably in the form of a film. preferable.

  FIG. 8 shows a structure for preventing corrosion and erosion in which an electrically insulating O-ring 23b is mounted in addition to the electrically insulating material 17F disclosed in FIG. The O-ring 23 b is mounted in an O-ring groove 23 a formed in the partition wall 15. When the pump is operated for a long period of time, the electrically insulating material 17F may break or peel from the casing ring 19 or the casing 15 due to vibration of the pump, impact during sliding, frictional heat, or the like. Even in this case, since the sealing performance is maintained by the O-ring 23b, the liquid is continuously maintained so as not to flow through the gap, and the casing ring 19 and the partition wall 15 of the casing are further reinforced so as not to make electrical contact.

  The O-ring groove 23a may be formed on either the casing ring 19 side or the casing 15 side. In this case, since the electrically insulating O-ring 23b is responsible for maintaining the sealing performance, the electrical insulating material 17F is not required to have much adhesiveness with the mating surface. However, when the O-ring 23b is used, it is assumed that the O-ring itself is crushed by a predetermined amount. The contact pressure applied by is not uniform. Therefore, the electrical insulating material 17F is formed with a thickness of 0.05 mm to 10 mm so that the casing ring 19 and the partition wall 15 of the casing do not contact even at one point and in order to receive the contact pressure applied to their mating surfaces. It is also desirable to insert it as a silicon-based or PTFE-based component.

  FIG. 9 shows a corrosion erosion prevention structure in which the outer edge of the casing ring 19a on the low pressure side, that is, the suction side flow path 11 side, extends outward in the radial direction of the pump shaft. This extending portion is an outer edge extension 19A. The casing ring 19 is divided into two parts, a first member 19a and a second member 19b. For this reason, even when the joining shape of the electrically insulating material 17G is complicated as shown in the figure, the first member 19a is disposed on the impeller 9 side, and the second member 19b is disposed on the suction side flow path 11 side. Can be assembled by fixing with screws 21.

  The above-described corrosion erosion prevention structure enables the assembly of the corrosion erosion prevention structure including the outer edge extension 19A even in a pump (such as a ring-cut type) in which the upper casing and the lower casing are not separated. The low pressure side of the second portion 19b of the casing ring 19 covers the partition wall 15 in a wide range. By doing in this way, even if the inlet back flow accompanied by cavitation occurs from the impeller 9 to the suction side flow path 11 during the low flow rate operation of the pump, the second portion 19b protects the partition wall 15, so that erosion progresses. Can be prevented. The second portion 19b of the casing ring 19 is made of a metal that is resistant to erosion, for example, stainless cast steel, and the partition wall 15 of the casing is less susceptible to erosion than the second portion 19b of the casing ring 19 but is made of a general-purpose metal, for example, cast iron. In addition, the partition wall 15 of the casing can be protected from cavitation erosion.

  The above description is described as a structure for preventing corrosion and corrosion of the pump. However, the present invention can also be defined as a method for manufacturing a pump. That is, a method of manufacturing a pump including a casing and an impeller, wherein the casing is provided, an electrical insulating material is provided at a predetermined position of the casing, and a predetermined casing ring facing the impeller is interposed via the electrical insulating material. The pump is installed in the casing. It should be noted that the various feature points described in the embodiment for carrying out the invention described above can be applied in combination with the manufacturing method of the pump.

  Further, the present invention can be defined as a pump repair method. That is, a method of repairing a pump including a casing and an impeller, wherein an electrical insulating material is provided at a predetermined location of the casing, and a predetermined casing ring facing the impeller is attached to the casing via the electrical insulating material. This is a repair method for the pump. The repair is performed after disassembling the pump once. It should be noted that the various feature points described in the embodiments for carrying out the invention described above can be applied in combination with the pump repair method.

  The present invention is not limited to the embodiment shown in FIG. 1 and FIG. 9, and is a pump that pressurizes and transfers a liquid, and a pump in which a casing and a casing ring (liner ring) are made of different metal materials is used for corrosion erosion countermeasure can do.

  The embodiment described above is described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the widest scope according to the technical idea defined by the claims. Moreover, each invention specific matter demonstrated by the said embodiment comprises this invention individually or in arbitrary combinations on the assumption that it is materialized as invention.

DESCRIPTION OF SYMBOLS 1 Pump 3 Upper casing 5 Lower casing 7 Rotating shaft 9 Impeller 9a Inlet part 10 Impeller ring 11 Suction side flow path 13 Discharge side flow path 15 Casing partition walls 17A, 17B, 17C, 17D, 17E, 17F, 17G Electrical insulation 19 Casing ring 19A Outer edge extension 21 Screw 23a O-ring groove 23b O-ring groove

Claims (5)

A pump for feeding liquid,
It has a corrosion and erosion prevention structure with a facing part of the casing and impeller,
The corrosion erosion prevention structure is
The casing;
A casing ring installed in the casing and facing the impeller;
An electrical circuit provided between the casing and the casing ring so that fluid does not pass between the casing and the casing ring from the high pressure side to the low pressure side and the casing and the casing ring do not contact each other. With insulation,
It said electrical insulating material is divorced system, seen at least Tsuo含of PTFE-based materials,
The electrical insulating material containing the silicon-based or PTFE-based material is a film-shaped molded product . 2. The pump according to claim 1, wherein a cross section of the corrosion / erosion prevention structure has a rectangular wave shape in which a shape of the casing and the casing ring in contact with the electrical insulating material is directed outward from the inside of the casing. A pump for feeding liquid,
It has a corrosion and erosion prevention structure with a facing part of the casing and impeller,
The corrosion erosion prevention structure is
The casing;
A casing ring installed in the casing and facing the impeller;
An electrical circuit provided between the casing and the casing ring so that fluid does not pass between the casing and the casing ring from the high pressure side to the low pressure side and the casing and the casing ring do not contact each other. With insulation,
A pump in which an O-ring for sealing is disposed between the electrical insulating material and the casing ring. The pump according to claim 2 , wherein the electrical insulating material includes at least one of a silicon-based material or a PTFE-based material . 4. The pump according to claim 3 , wherein a cross section of the corrosion erosion prevention structure is a rectangular wave shape in which a shape of the casing and the casing ring in contact with the electrical insulating material is directed outward from the inside of the casing .

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